1. Field of the Invention
The present invention relates to an image-forming apparatus, such as a mono-chrome/full-color copying machine, a printer, a facsimile and a composite machine thereof.
2. Description of the Related Art
In an image-forming apparatus of an intermediate transfer system in which toner images of respective colors, formed on latent-image supporting members, are respectively primary-transferred, and superposed on an intermediate transfer member, and then secondary-transferred onto a image-receiving medium at one time. Such an image-forming apparatus causes a slight amount of residual toner on the intermediate transfer member upon secondary-transferring. For this reason, a method in which an elastic blade made of rubber or the like is made in contact therewith as a cleaning means for removing the residual toner has been widely used.
In order to improve the secondary transferring rate, a method is proposed in which a hard releasing layer is formed on the surface of the intermediate transfer member so that the releasing property to toner is improved. In such an image-forming apparatus, however, although the secondary-transferring efficiency is improved, insufficient cleaning occurs to cause residual toner on the intermediate transfer member, even when a cleaning blade is used. More specifically, since the hard releasing layer on the surface of the intermediate transfer member is formed so as to make toner more easily separated, a frictional force exerted onto the blade becomes lower in comparison with the surface of a conventional intermediate transfer member without a hard releasing layer. For this reason, the edge portion of the cleaning blade is not drawn in the moving direction of the intermediate transfer member, but is allowed to slide on the surface, with the result that insufficient cleaning, such as escaped toner, tends to occur. In particular, in a low temperature environment, the occurrence of insufficient cleaning becomes conspicuous. In the case when toner having a spherical shape with a small particle size is used so as to form a high-quality image, that is, for example, in the case when a polymerized toner is used in combination, the occurrence of insufficient cleaning becomes conspicuous. When the contact pressure of the cleaning blade against the intermediate transfer member is increased so as to ensure the frictional force against the intermediate transfer member, edge damage (chipping) in which the edge portion of the cleaning blade is damaged tends to occur.
From the viewpoint of an improved cleaning characteristic of a photosensitive member and a conventional intermediate transfer member, the application of a cleaning blade having an impact resilience coefficient of 20% or more at 10° C. and in the range from 70% or less at 40° C., a 300% modulus of 200 kg/cm2 or more, and a tear strength of 70 kg/cm or more has been proposed (Japanese Patent-Application Laid-Open No. 2003-167492), and the application of a cleaning blade having an impact resilience coefficient of 35% or more at 10° C., with a rate of change in the impact resilience within a temperature range from 10 to 40° C. being set to 1.4/deg or less has also been proposed (Japanese Patent-Application Laid-Open No. 2004-151206).